Ion-exchange resins containing quaternary ammonium hydroxide groups



United States PatentO ION-EXCHANGE RESlNS CONTAINING QUATER- NARYAMMONIUM HY DROXIDE GROUPS Gaetano F. DAlelio, Pittsburgh, Pa., assignorto Koppers Company, Inc., a corporation of Delaware No Drawing.Application December 5, 1951, Serial No. 260,081

9 Claims. (Cl. 260-21) 7 This invention relates to new anion-exchangeresins. More particularly it relates to the preparation of anionexchangeresins having quaternary ammonium hydroxide groups.

Ion-exchange resins have been found desirable for a wide variety ofcommercial uses. For example, such resins are being used in thepurification, deionization, or softening of water, the recovery ofmagnesium from sea water and brine, the recovery of copper and ammoniafrom waste cuprammonium solutions in rayon plants, the recovery of aminoacid from protein hydrolyzates, recovery of certain vitamins fromsolutions, the separation of fission products obtained from uranium andplutonium, the separation of rare earths, the removal of sodium andcopper from oils, the removal of iron and copper from acid liquors,various applications in analytical determinations and in catalyzingesterification, ester hydrolysis, sucrl'ose inversion, etc., and evenfor the treatment of peptic u cers.

Anion-exchange resins used for some of these purposes are disclosed inapplicants U. S. Patent 2,366,008, as signed to the General ElectricCompany, which comprise aminatecl copolymers of mono-vinyl-aromaticcompounds and divinyl-aromatic compounds, such as prepared by thenitration of an insoluble, infusible styrene-divinyl benzene copolymerfollowed by reduction of thenitro groups to amino groups. are availablecomprise phenylene diamine-formaldehye resins, and thephenol-formaldehyde-diethylene-triamine and triethylene-tetraamineresins, etc. However, the efficiency of these resins is not suflicientlysatisfactory for many anion exchange purposes.

Anion-exchange resins of great utility have now been found whichcomprise water-insoluble, infusible resins containing quaternaryammonium hydroxide groups, the resins comprising polymers having aplurality of units of the formula where X is hydrogen or a quaternaryammonium hydroxide group of the formula CH2NR'3OH wherein X, R and R areas above-described.

Thus, the resins of this invention may be regarded as having thefollowing monomer structure, although the resins can advantageously beprepared indirectly from other types ofmonomers as illustratedhereinafter.

Other anion-exchange resins which 2,697,079 Patented Dec. 14, 1954 Thequaternary ammonium hydroxide resins of this invention can be preparedby a number of methods. For example, certain polymerizable monomers canbe polymerized directly to resins having quaternary ammonium hydroxidegroups. Thus, a typical resin may be considered as derived by thepolymerization of allyl-trimethyl ammonium hydroxide A resin of thisbasic structure can be prepared by the polymerization of acrylonitrile,advantageously with a crosslinking agent, and subsequent reduction andexhaustive alkylation of the polymer to give the same type of resinhaving quaternary ammonium hydroxide groups. Similar quaternary ammoniumhydroxide resins can also be prepared by the indirect method frommethacrylonitrile, t'umaronitrile, ethacrylonitrile, etc., that is, fromcyano compounds having the formula wherein Y is hydrogen or a cyanogroup; and R is hydrogen or a methyl or ethyl group.

in most cases the polymerizable monomer, or mixture of polymerizablemonomers, which contains the quaternary ammonium hydroxide group, or agroup convertible thereto, is converted to an insoluble, intusible resinby copolymenzation with one or more cross-linking agents. Cross-linkingagents which are not necessarily equivalent but which are suitable forthe purpose of this invention include various classes ofhydrocarbon-type cross-linking agents, e. g., those having a hydrocarbonnucleus, with or without nonhydrocarbon substituents attached thereto,such as divinyl aryls, e. g., divinyl benzenes, divinyl naphthalenes,divinyl toluenes, divinyl xylenes, divinyl chlorobenzenes, divinyldiphenyls, etc., or other hydrocarbontype cross-linking agents, such asbutadiene, chloroprene, isoprene, cyclopentadiene, isopropenyl styrenes,diisopropenyl benzenes, vinyl cyclohexene, l-phenyl-butadiene, 2-phenyl-butadiene, etc. Any substituents attached to the hydrocarbonnucleous of these cross-linking agents should be such as will notinterfere with any of the steps of preparation or use of theanion-exchange resins. When these hydrocarbon-type cross-linking agentsare used, it is generally advantageous to use about 2-25 per cent byweight of the cross-linking agent. In some cases, however, insolubilityand infusibility may be imparted to the resin by the use of a monomerwhich has or will give the structure shown in the formula above andwhichalso has more than one polymerizable group, e. g., by starting withcyano-butadienes, etc., which can be used alone or with other monomershaving quaternary ammonium hydroxide groups or groups which can beconverted thereto.

In other cases, it is even possible to have the crosslinking effected byan alkylene or aralkylene group connecting two polymer chains byattachment to a nitrogen in each chain. Generally, this type ofcross-linking may not be preferred since some of the quaternary ammoniumhydroxide groups are thereby restricted in their movements and aretherefore not so easily accessible for anionexchange activity. Thelatter type of cross-linking may be accomplished, during or subsequentto the exhaustive alkylation, either by use of a polychloroalkyl,- arylpolychloroalkyl, or polychloroalkylaryl compound, such asdichloroethylenc, phenyl di chloroethylene, di-(chloromethyl)-benzene,etc., or by the use of a polyhydric alcohol as a solvent in thereduction of a cyano group to an amine. Moreover, it is oftenpermissible to have somewhat similar cross-linking accomplished by theformation of secondary amines, sometimes during the reduction of cyanogroups, etc., to give ultimately cross-linking of the type In thislatter event, an R' of the formula becomes a R CHr( J group.

In the preparation of these quaternary ammonium hydroxide resins frompolymers containing cyano or other groups reducible to amino groups, anyconvenient method of hydrogenation may be used to convert thenitrogencontaining groups to amino groups. Such hydrogenations may beactivated by various Well-known hydrogenation catalysts includingpalladium on charcoal, Raney nickel, platinum, cobalt, nickel, copper,aluminum, iron, zinc, etc. With some compounds such as alkyl cyanides,alkyl oximes and alkyl hydrozines, reduction to amines may beaccomplished by the use of sodium and an alcohol such as ethanol.Moreover, iron and water catalyzed by ferrous chloride may be used toreduce nitro compounds to amines. In some cases, exhaustive or partialalkylation may be carried on simultaneously with the reduction by theuse of alcohol solvents corresponding to the alkyl or aralkyl groupdesired for the alkylation.

For certain purposes which do not require anionexchange resins of thehighly basic character of the quaternary ammonium hydroxide resins, theintermediate amine resins of this invention can be used quitesatisfactorily. These amine resins can be regarded as having repeatingunits of the structure wherein Z is hydrogen or a CH2NR"2 group; R ishydrogen or a methyl or ethyl group; and R is hydrogen or an alkyl oraralkyl group. Thus, copolymers of acrylonitrile, methacrylonitrile,fumaronitrile, ethacrylonitrile, etc., when reduced to the correspondingamino compounds give water-insoluble, anion-exchange resins such ascrosslinked polyallyl amine, polymethallyl amine, polyaminomethylpolymethylene (polymerized 1,4-diamino-butene2 or1,Z-bis-amino-methyl-ethylene), polyethallyl amine, etc. Moreover, thepartially substituted amine intermediates have utility as anion-exchangeresins, e. g., the mono-, diand tri-substituted amines such as mono-,diand tri-methyl derivatives of polyallyl amine, polymethallyl amine,polyaminomethyl polymethylene, polymerized ethallyl amine, etc. Withsuch amine intermediates which are to be used per se as anion-exchangeresins, the cross-linking agents may be of the same type describedhereinbefore as satisfactory for the quaternary ammonium hydroxideanion-exchange resins.

Where exhaustive alkylation of an amine is to be effected, this isaccomplished by heating the amine with a slight excess of the propernumber of molecular equivalents of alkyl halide or substituted alkylhalide selected to give the desired R group. The tetraalkyl ammoniumsalt thus produced is converted to the tetraalkyl ammonium hydroxide byreaction with alkaline reagents, such as aqueous or alcoholic sodiumhydroxide or potassium hydroxide, aqueous sodium carbonate, etc. Afteranionadsorption, the exhausted resin may be regenerated by the use ofthe same type of alkaline solutions as used in the original conversionof the quaternary ammonium salt to the hydroxide.

Minor portions of certain other monomers such as isobutylene, styrene,chlorostyrene, etc., may be used with the aforementioned monomers.However, these latter monomers should not have functional groups whichwill interfere with the polymerization activities of the monomers orwith the ion-exchange activity of the products, or which may be rupturedto give substantial decrease in length of monomer chains or incross-linking. Moreover, the cross-linking agent which is used shouldnot contain any such interfering functional groups.

Since the quaternary ammonium hydroxide groups are the activeion-removing groups in these products, it is advantageous that the majorportion of the polymerization mixture be of polymerizable monomerscontaining quaternary ammonium hydroxide groups or groups convertiblethereto. Instead of starting with a monomer mixture containing thecross-linking agent, it is also possible to add the cross-linking agentto partial polymers of these monomers and to effect cross-linking bysubsequently completing the polymerization.

The following examples illustrate more particularly the above-describedmethods for preparing ion-exchange resms.

Example I Into a glass container are placed 7 parts of Turkey red oil,300 parts of distilled Water, 0.7 part of benzoyl peroxide, parts offreshly distilled acrylonitrile and 10 parts divinyl benzene in theorder named. The glass container is closed with a seal lined withaluminum foil and is revolved in a water bath heated at about 60 C. forabout 30 hours. The peroxide polymerization catalyst is destroyed byadding about one part of a 10% aqueous solution of hydrazine. Thedispersion is then transferred to a high pressure autoclave fitted witha stirrer and 5 parts of Raney nickel (see U. S. Patent No. 1,628,190)is added thereto along with 30 parts of concentrated aqueous ammonia.The contents of the autoclave are then heated with rapid stirring at C.to C. While maintaining a pressure of 750 pounds per square inch withhydrogen. The treatment is continued until absorption with hydrogenceases. The insoluble, cross-linked polymer containing primary aminegroups obtained by hydrogenation of the cyano groups is separated byfiltration.

These amine groups are converted to the quaternary ammonium bromide formby suspending the resin in ethyl bromide in a container equipped with areflux condenser and refluxing the mixture for approximately 24 hours.The resin containing the quaternary ammonium bromide groups is separatedfrom the ethyl bromide by filtration and washed with a small volume of avolatile organic solvent such as diethyl ether. Upon treatment of thisresin with approximately /3 normal sodium hydroxide solution, there isobtained the quaternary ammonium hydroxide form of the resin.

Example 11 One hundred parts by weight of the resin of Example I is wetWith 50 parts by Weight of distilled water, and then 100 parts by Weightof a standardized hydrochloric acid solution is added With shaking.After the resin and the solution have been in contact for about 15minutes, the solution is separated from the resin by filtration. Thefiltrate solution is then titrated with sodium hydroxide to determinethe amount of hydrochloric acid still in solution. If the filtratesolution has been completely neutralized by the resin, the procedure isrepeated using a larger amount of the hydrochloric acid solution With afresh sample of the resin. The efiiciency of the resin is determined bycalculating the ratio of chloride ions actually removed from thesolution to the chloride ions theoretically removable. A good efficiencyis indicated by these calculations.

Example 111 The exhausted resin of Example II is regenerated bytreatment with about /3 normal sodium hydroxide solution. After thesolution is removed by filtration the resin is washed well withdistilled water and retested for its anion-adsorption capacity accordingto the above-mentioned procedure. The efficiency after regenerationapproximates the original capacity of the resin.

Example IV Into a glass container are placed 7 parts of Turkey red :inthe order named. Theglass container is closed with a seal lined withaluminum foil and is revolved in a water bath heated at about 60 C. forabout 30 hours. A stable latex of polymethacrylonitrile is obtained. Theperoxide polymerization catalyst is destroyed by adding, about one partof a 10% aqueous solution of hydrazine. The dispersion is thentransferred to a high pressure autoclave fitted with a stirrer and 5parts of Raney nickel (see U. S. Patent No. 1,628,190) is added theretoalong with 30 parts of concentrated aqueous ammonia. The contents of theautoclave are then heated, with rapid stirring, at 135 C. to 145 C.while maintaining a pressure of about 750 pounds per square inch withhydrogen. The treatment is continued until absorption of hydrogenceases. The aqueous product is then boiled to remove ammonia. The wateris removed by distillation under vacuum and cross-linking of the linearpolymer chains is elfected by treating the resin with parts1,2-dichloroethane at reflux temperature. There is obtained a waterinsoluble resin cross-linked through a portion of the amino nitrogenatoms of the resin.

This resin is admixed with excess ethyl bromide and maintained at refluxtemperature for approximately one day to effect exhaustive alkylation.There is obtained the quaternary ammonium bromide form of the resin. Treatment with approximately 4/3 ammonium hydroxide yields the quaternaryammonium hydroxide form of the resin.

This resin is tested by-the procedures outlined in Examples II and IIIand efiiciency of slightly less than that of the resin described inExample I is indicated.

Example V To 90 parts allyl trimethyl ammonium hydroxide and 10 partsdivinyl benzene is added 1 part benzoyl peroxide and the mixture ismaintained at 60 C. for about one week. The insoluble, infusible resinwhich is obtained is comminuted and is tested according to theprocedures outlined in Examples II and III. A good efliciency isindicated.

The quaternary ammonium hydroxide resins of this invention are veryeflicient anion-adsorption agents due very likely to the highly basiccharacter of the quaternary ammonium hydroxide groups. Other anionswhich may be removed from solution by the water-insoluble polymers ofthis invention, in addition to the chloride anions previously mentioned,include nitrate ions, sulfate ions, acetate ions, oxalate ions, tartrateions, or any other anions which will react with the basic quaternaryammonium hydroxide groups in the resin to form insoluble salts.Apparently because of the highly basic character of the quaternaryammonium hydroxide groups, these resins are more efiicient than thepreviously used amine-type anion-exchange resins. These anion-exchangeresins can be readily regenerated by washing with a dilute alkalisosolution, preferably of an alkali-metal hydroxide which forms solublesalts with the adsorbed anions.

The cross-linked copolymers suitable for the practice of this inventioncan be prepared by any method which will give infusible, insolubleresins, for example, by mass, solution, emulsion or suspensionpolymerization. The polymerizations may be advantageously catalyzed byvarious types of catalysts, such as peroxides, e. g., benzoyl, hydrogen,acetyl, acetyl-benzoyl, phthalyl, lauroyl peroxides,tert-butylhydroperoxide, etc.; other per-compounds, e. g., ammoniumpersulfate, sodium persulfate,

sodium perchlorate, etc.; and in some cases the Friedel- Crafts typecatalysts, such as aluminum chloride, advantageously at lowtemperatures.

Inert material, such as diatomaceous earth, alundum, coke, silica,cinders, porous glass, etc., may be used as a carrier for the resin inorder to increase the effective surface of the resin for ion-exchange.These carriers may be introduced by adding them any time prior tocomplete polymerization of the monomers to an infusible, insolublestate. An emulsion or dispersion type of polymerization is advantageousfor the coating of such carrier materials with the resin.

This application is a continuation-in-part of application Serial Number117,728 filed September 24, 1949, now abandoned.

The invention as hereinbefore set forth is embodied in particular formand manner but may be variously embodied within the scope of the claimshereinafter made.

1. A water-insoluble resincomprising a polymer having a plurality ofrepeating units having the structure copolymerizable divinyl arylcompound and at least one polymerizable monomer of the formula wherein Xis a member of the class consisting of hydrogen and --CH2NR'3OH groups;R is a member of the class consisting of hydrogen and alkyl groups ofless than 3 carbon atoms; and R is a member of the class consisting ofalkyl and aralkyl groups.

3. A water-insoluble resin of claim 1, in which the divinyl arylcompound is divinyl benzene.

4. A process for preparing water-insoluble anion-exchange resinscomprising the steps of exhaustively alkylating with an agent capable offurnishing groups chosen from the. class consisting of alkyl and aralkylgroups the amino groups in a polymeric amine and thereafter convertingthe resultant quaternary ammonium salt groups to quaternary ammoniumhydroxide groups, said polymeric amine containing repeating units havingthe structure wherein Z is a member of the class consisting of hydrogenand --CH2-NR"2 groups; R is a member of the class consisting of hydrogenand methyl and ethyl groups; and R" is a member of the class consistingof hydrogen and alkyl and aralkyl groups, and in which the polymericamine has been cross-linked by a copolymerized divinyl aryl compound.

5. A process of claim 4, in which the polymeric amine has beencross-linked by a divinyl benzene.

6. process of claim 4, in which the polymeric amine contains repeatingunits having a structure identical with allyl amine.

7. A process of claim 6, in which the polymeric amine has beencross-linked by a divinyl benzene.

8. The method of treating liquid media to remove anions therefrom whichcomprises contacting said media with a water-insoluble resin comprisinga polymer having a plurality of repeating units of the structure Ji AH:

r m'aon' wherein X is a member of the class consisting of hydrogen andquaternary ammonium hydroxide groups of the formula -CH2NR'3OH; R is amember of the class consisting of hydrogen and methyl and ethyl groups;and R is a member of the class consisting of alkyl and aralkyl groups,and in Which said polymer has been cross-linked by a copolymerizeddivinyl aryl compound.

9. The method of claim 8, in which the polymer has been cross-linked bycopolymerized divinyl benzene.

(References on following page) UNITED STATES PATENTS 2,591,573 McBurney'Apr. 1, 1952 Number Name Date I 2,228,514 Griessbach DJan. 12, 5 OTHERREFERENCES 2,366,008 DAlelio ec. 2 r 2,456,428 Parker 14, 1948slgiltggtggrjrrlglzg. Chem. Soc., vol. 71, pages 3120- 2,481,768 MillsSept. 13, 1949 P nan-Q

1. A WATER-INSOLUBLE RESIN COMPRISING A POLYMER HAVING A PLURALITY OFREPEATING UNITS HAVING THE STRUCTURE